This invention relates to a separable element which can be severed instantaneously for various purposes. More particularly, it relates to a separable connecting element such as a pyrotechnic bolt-type fastener, which can be fused or melted with little or no noise and provides the capability of utilizing the pressure developed by the resultant heat and products of combustion to perform actuation of a device.
Severable elements which can fasten a plurality of items together, are widely used in connection with space missiles, rocket boosters, multi-stage rockets, commercial vehicles, cranes, ships, submersible mines and valves, and in other applications where instantaneous separation of two or more elements is required. Present explosive devices, and particularly explosive bolts, are subject to the disadvantages that the explosion separating or breaking them is accompanied by noise, shock, production of loose and flying parts and the expulsion of propellant gases into the system or into the atmosphere.
The noise and shock resulting in the escape of propellant by-products from the partially opened severable element is severe enough to disrupt electronic circuits, break communication lines, rupture liquid carrying pipes, causing malfunction or even failure of the device with which the explosive bolt is used. In the case of a flooding valve for a mine or other underwater device the noise produced by the shock waves would be highly deleterious in areas where detection by mine countermeasures would not be desired. The release of gaseous by-products into an ambient environment may also be objectionable in many space, surface and underwater devices as these by-products can contaminate the environs of the device and are capable of building up corrosive by-products on critical items such as wires, tubes, mirrors, electrical control mechanisms and other critical and sensitive elements.
Previous methods which have used detonating chemicals for actuation are typified by U.S. Pat. No. 3,530,759 to Francis, U.S. Pat. No. 3,254,555 to Joneikis, and U.S. Pat. No. 3,200,706 to Kinard. However, the detonating chemicals in Francis represents a safety hazard, particularly during storage, and in Joneikis and Kinard, the generation of actuation noise during detonation of an explosive charge is pronounced and unavoidable. Some methods, e.g., U.S. Pat. No. 3,728,934 to Palmer, have attempted to provide an irreversibly severable linkage which is fused or destroyed by a thermite mixture thus eliminating the use of detonating chemicals. Unfortunately, Palmer does not confine the products of combustion nor does he produce a motive fluid useful for doing work. Also, Palmer's design does not appear to readily lend itself to a system requiring relatively high tensile loads.
A requirement thus exists for a relatively strong low noise level means of quickly separating a fastener on electrical command which can also produce sufficient high pressure gas to perform actuation of a device. The present invention achieves all of these objectives while avoiding the deficiencies of the prior art mechanisms.